Method of making tube



Dec. 17, 1957 METHOD OF MAKING TUBE Filed July 14, 1955 R. H, HoBRocKINVENTOR.

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United States Patent O This invention relates to the method of makingytube` fromstrip metal? stock and it is-directed particularly tok themakingof tubel where the strip is moved-lengthwise, fashioned intotubing with interfacial portions, and the interfaces united by a bondingmetal which has been rendered-l molten.v

Muchtubing of this type has been made fromv strip ste'el1 stock;`wherein the interfaces` are united by copper The principal objectv ofthis linvention is toy provide` aY processfor making tube from barestrip stock thus dispensing withthe necessity of applying the bondingmetal t'othe strip in the form of a coating or film. Inv accordaneewiththe' invention the bondingmetal isy introduced intothe tube in the formof a strip or wire. The tube is subjected to a heat treatment to meltthe' bonding metal-.- The principal difficulty encountered is thattubing so fashioned and which is round in cross section twists on itsaxi's; This is due apparently to different metal conditions as torelative hardness and softness and to various strains set up in themetal. As a result, the seam' running lengthwise of the tube changes itsposition.

When the strip or wire of bonding metal is rendered molten, itgravitates to the bottom of the tube, and if the seam is at the bottomof the tube, the bonding metal will iiow between the interfaces to unitethe interfacesy upon solidication. However, if the tube twists so thatin different longitudinal increments of the-tube the seam is displacedupwardly from the bottom of the tube, the molten metal cannot iiow inbetween the interfaces.

In accordance with this invention the tubing is made inan invertedmanner so that the seam is normally positioned lowermost. Andfurthermore, the tube is fashioned into a non-circular form in crosssection so that it canbe guided and held in a position with the seam atthe lower portionof the tube so that molten metal may iiow in. betweenthe interfaces. Preferably, the tubing thus formed in an inverted manneris fashioned so that it is of elongate form in cross section with thelong axis disposed substantially vertically and the short axis disposedsubstantially horizontally. After the bonding of the interfaces, thetubing is preferably subjected to a treatment to give it a substantiallyround or circular form in cross section.

The invention is disclosed in the accompanying drawings:

Fig. 1 is a general View indicating an apparatus s well as method forfashioning the tube in accordance with the invention with continuouslengthwise movement of the strip through a tube forming mill, a heatingzone, ay cooler, and arounding unit.

Fig. 2 is a cross sectional view taken substantially on line 2--2 ofFig. 1 illustrating an early stage of the fashioning of the strip.

Fig. 3 is a cross -sectional view taken substantially on lin'e -3-3 ofFig. 1 showingy nal forming rolls.

Fig 4v is a cir-oss sectional view taken oriy line 4-4 of Fig.y 'lshowing theftube as formed.

2,816,356 Patented Dec. 1.7,- 1957 ICC Fig. 5 is ai sectional viewtakeny on line 5-5 ofvFig. 1 illustrating the cooler.

Fig. 6 is a sectional view takenon line 6--6 ofaFig, 1` illustratingsizing and rounding rolls.

Fig.Y 7y is a view illustrating a furnace through which a plurality oftubes may be passedffor heatingthe same.

Fig. 8 is an enlarged-sectional View taken substantial ly on line 8 8ofFig. 7y illustrating a guide pipe inithe furnace.

Referring first to Figi- 1, the strip 1 is drawnv fromM a supply coil 2andit is passedwith lengthwise movement through a tube mill 4. The tubemill has forming rolls which fashions the strip transversely into hollowcross sectionall form. The strip is formed about Va mandrell 6 (Fig. 2),which is held by a bracket 8. This mandrel is hollow and a strip. orwire 10 ofbonding metal. is drawn from a supply roll -11 and' fed intothe mandrel. In Fig. 2 an early stage of the formation of the strip isindicated as well also as-the mandrel and the bonding metal within thevhollow mandrel. The strip is` preferably of steel and the bonding metalpreferably of cop'- per. However, other metals may be employed: Forexample, steel strip may be used`V with a bonding metalof solder, eitherhard or soft solder; the strip maybe Monel metal" with an appropriatebonding metal.-

T he tube mill may be one of rather conventional form but' the rolls aregrooved to form the strip intoelon# gate' hollow cross sectionalshape.The final rolls of the tubernill are shown at 15 and-16 andv itwill beseen in Fig. 3- that the mandrel has an elongate cross sectionalform-andV that the rollsV 15 and -16' are grooved so as to form or wrapthe metal of the strip with the elongate cross sectional form. The tubeillustrated' is one fashioned froml a single strip of stock wherein thestock is rolled or fashioned through about 720 with the` edges thereofbevelled or scarfed and' fittedagainst an offset in theintermediateportion ofthe strip.v The t-ube is generally illustrated atT in Fig. 4, the outsider edge-raft 17 and the inside edge at 18'. Theinner and outer pliesof the tube are formedI in tight interfacialenga-gement and the llocation where the edges 17. and 18 engage'opposite sidesl of the intermediate part ofthe strip maybe consideredthe seam. The interfaces between the body of the strip and the edge 18intersect theinner lsurface of the tube. The tube thus kformed can beguided' and held so that the seam is held lowemiost or, in7 other words,at the lower terminal of the long axis.

In Fig. 1 the strip -and-l tube are moved continuously and as the tubeemerges from the tube mill it enters ahe'ating zone. This may bel in theform of a housing. 20" into which a non-oxidizing or reducing gas maybeV entered through a pipe 21. This heating zone is 'of the electricalresistance variety. There are three roller electrodes 2v2, 23 and 24with backup rolls' 25, 26 and' A transformer has a' primary 33connectedv to `a suitable source of electrical current. One side of thesecondary Z8 is connected to the electrode roller 23 by a conductor 30.The other side of the secondary is connected to the" electrode 22 by aconductor 31` and to the electrode 24 by a conductor 32. By connectingone side of the sectondary to the two outside electrodes the problemsdof:

The' metal will not iloW out from-between the'inter'f'aeesf 3 whichintersect the outer surface of the tube at the edge 17 because thecaoillarv snare ceases at that point.

The tube leaves the heating zone and enters a cooler generallv indicatedat 35. This cooler is preferably of the iacketed tvoe having an outercasing 36. and an inner casing 37. through which the tube travels. Theinner tube or iacket 37 mav be shaped, particularly for a portion of itslength. to guide the tube and hold the seam down. However. after thebonding metal has solidified there is no further need of guiding thetube in the cooler but. of course. it is engaged and held positioned bythe rools of the sizing and rounding unit. Coolingl water may be passedbetween the iackets and may bei introduced through a pine 40 anddischarged from pipe 41. The gas introduced through the pipe 21 may flowboth upstream and downstream with some of the gas burning oft` at theinlet to the heating chamber and some discharging from the outlet end ofthe cooler.

With continuous movement the tube now passes through a sizing androunding unit generally illustrated at 44. It comprises a series ofsuitably formed rolls which engage the tube and change its elongatecross sectional form into rounded form. The final rolls are indicated at45 and 46 and the tube is given a circular or rounded form as indicatedin Fig. 6. In the process just described, the strip moves successivelythrough the forming mill, the heating zone, the cooler, and the roundingand sizing unit. The strip may move at fairly high speed because it canbe rapidly heated by electrical resistance. However, the method may becarried out by separating the heating unit and cooling unit from thetube mill and rounding unit. A suitable furnace is shown in Fig. 7 at 50through which a plurality of tubes may be simul taneously passed. Thetubes may be fed into the furnace by driving rollers 51 and S2. Thefurnace is suitably heated to raise the temperature of the tubes andmelt the copper `inside the same. As the tubes pass from the furnacethey pass into cooler tubes 53 and when cooled to the point where theymay be introduced to the atmosphere without objectionable oxidation theymay pass out onto a support 54. The furnace may be supplied with anon-oxidizing or reducing gas through an inlet pipe 55 and this gas mayescape from the inlet of the furnace and the outlet of the cooler.

The furnace is provided with a guide pipe for each tube. Such a guidepipe is shown in Fig. 8 at 56. It will be noted that the guide pipe isof elongate form 1n cross section to more or less fit the tube. Inpracticing lthe method of this invention with the furnace 50, the tubemill is separated from the furnace and tubes are formed rapidly therebyand cut into lengths. A plurality of the tubes are passed simultaneouslythrough the furnace 50. The tubes pass through the furnace ft muchslower than they are made in the tube mill but by passing a plurality oftubes simultaneously through the furnace, the overall output of thefurnace may substantially correspond to the `output of the tube mill.After the tubes pass through the furnace and are cooled they may then bepassed through the rounding and sizing unit 44 which, of course, in thisinstance, will not be necessarily inline with the tube mill.

In either case, the tube of elongate form lin cross section can be heldwith facility so that the seam is maintained lowermost. Thus, when thewire or strip of bonding metal is rendered molten, it has access to theinterfaces where the interfaces intersect the inside surface of thetube. When the system is used with the resistance heating zone, as shownin Fig. 1, thc electrodes and the back up rollers serve to hold the tubein proper position. When the tubes are passed through the furnace 50 therespective guide pipes hold the tubes in proper position. It is notnecessary to the invention that the seam in all increments of the tuberemain accurately at the lower terminal of the long axis of the elongateform. It is .4 sutiicient that the seam be held suiciently near the lowermost lportion of the tube or, in other words, near the lower terminalof the long axis to permit the molten copper to have access thereto andthus flow in between the interfaces. The terminology in the claimsappended hereto are to be read with this interpretation.

I claim:

1. The method of making tube from strip metal stock comprising, movingthe strip lengthwise, fashioning the strip into tubing of elongate formin cross section with the long axis disposed substantially vertically,bringing the edges of the strip into proximity with each other and withinterfacing portions substantially at the lower terminal of the longaxis, feeding a strip ofbonding metal into the tube interior as it isbeing formed, passing the tube through a heating zone to melt thebonding metal, while utilizing the elongate form of the tube as a guidemeans for maintaining said edges substantially at the lower terminalpart of the long axis, whereby the molten bonding metal, whichgravitates to the lower portion of the elongate form, flows bycapillarity between the interfaces, and cooling the tube to solidify thebonding metal and unite the interfaces.

2. The method of making tube from strip metal stock comprising, movingthe strip lengthwise, fashioning the strip into tubing of elongate formin cross section with the long axis disposed substantially vertically,bringing the edges of the strip into proximity with each other and withinterfacing portions substantially at the lower terminal of the longaxis, feeding a strip of bonding metal into the tube interior as it isbeing formed, passing the tube through a heating zone to melt the'bonding metal, while utilizing the elongate form of the tube as a guidemeans for maintaining said edges substantially at the lower terminalpart of the long axis, whereby the molten bonding metal, whichgravitates to the lower portion of the elongate form, flows bycapillarity between the interfaces, cooling the tube to solidify thebonding metal and unite the interfaces, then treating the tube to changethe elongate cross sectional form to a substantially round form.

3. The method of making tube with a double thickness wall from stripmetal stock which comprises, moving the strip stock lengthwise,fashioning the strip into tubing of elongate form in cross section withthe long axis disposed substantially vertically, and with inner andouter plies in interfacial relationship, bringing edge portions of thestrip stock into proximity with each other substantial at the lowerterminal of the long axis, feeding a strip of bonding metal into thetube interior as it is being formed, passing the tubethrough a heatingzone to melt the bonding metal, while guiding the tube through theagency of its elongate fornito maintain said edges substantially at thelower `terminal of the long axis, whereby the molten bonding metal,which gravitates to the lower portion of the elongate form, flows bycapillarity 'between the interfaces, cooling the tube to solidify thebonding metal and unite the interfaces, then treating the tube to changethe elongate cross sectional form to a substantially round form.

4. The method of making tube with a double thickness wall from a singlestrip of metal `stock which coinprises, moving the strip lengthwise,fashioning the strip into tubing of elongate form in cross section withthe long axis disposed substantially vertically, and with inner andouter plies in interfacial relationship, bringing thev edges of thestrip into proximity with each other on opposite sides of theintermediate part of the strip and substantially at the lower terminalof the long axis, feeding a strip of bonding metal into the tubeinterior as it is being formed, passing the tube through a heating zoneto melt the bonding metal while utilizing the elongate forrn of the tubeto guide the tube to maintain said edges susbtantially at the lowerterminal of the long axis, whereby the molten bonding metal whichgravitates to the lower portion of the elongate form, flows 'bycapillarity between the interfaces, cooling the tube to solidify thebonding metal and unite the interfaces, and then treating the tube tochange the elongate cross sectional form to a substantially round form.

5. The method of making tube with a double thickness wall from a singlestrip of steel stock which comprises, moving the strip lengthwise,fashioning the strip into tubing of elongate form in cross section withthe long axis disposed substantially vertically, and with inner andouter plies in interfacial relationship, bringing the edges of the stripinto proximity with each other on opposite sides of the intermediatepart of the strip and substantially at the lower terminal of the longaxis, feeding a strip of copper into the tube interior as it is beingformed, passing the tube through a heating zone to melt the copper whileutilizing the elongate form of the tube to guide the tube to maintainsaid edges substantially at the lower terminal of the long axis, wherebythe molten copper which gravitates to the lower portion of the elongateform, ows by capillarity between the interfaces, cooling the tube tosolidify the copper and unite the interfaces, and then treating the tubeto change the elongate cross sectional form to a substantially roundform.

6. The method of making tube from strip metal stock comprising, movingthe strip lengthwise, fashioning the strip into tubing of elongate formin cross section with the long axis disposed substantially vertically,bringing the edges of the strip into proximity with each other and withinterfacing portions substantially at the lower terminal of the longaxis, feeding a strip of bonding metal into the tube interior as it isbeing formed, passing the tube with continuous movement through aheating zone to melt the bonding metal, while maintaining said edgessubstantially at the lower terminal part of the long axis by utilizingthe elongate form of the tube as a guide means, whereby the moltenbonding metal, which gravitates to the lower portion of the elongateform, ows by capillarity between the interfaces, cooling the tube tosolidify the bonding metal and unite the interfaces, then treating thetube to change the elongate cross sectional form to a substantiallyround form.

7. The method of making tube from strip metal stock which comprises,fashioning the strip into tubing of elongate form in cross section withthe long axis disposed substantially vertically, bringing the edges ofthe strip into proximity with each other substantially at the lowerterminal of the long axis to form interfacial portions, placing a stripof bonding metal into the tube interior, passing the tube through aheating zone to melt the bonding metal, while utilizing the elongateform of the tube for guiding the tube to maintain said edgessubstantially at the lower terminal of the long axis, whereby the moltenbonding metal, which gravitates to the lower portion of the elongateform, flows by capillarity between the interfaces, cooling the tube tosolidify the bonding metal and unite the interfaces, and then treatingthe tube to change the elongate cross sectional form to a substantiallyround form.

8. The method of making tube from strip metal stock comprising, movingthe strip lengthwise and fashioning it into tubing of acircular crosssection with the strip edges in proximity with each other to form a seamarea having interfaces generally at the lowermost portion of the tube,introducing a body of bonding metal into the tube interior `as it isbeing formed and, while utilizing the acircular shape of the tube as aguide means to maintain said seam area generally at its lowermostportion, passing the tube through a heating zone to melt the bondingmetal, so that the molten bonding metal g-ravitates to the seam area andflows by capillarity between the interfaces, and cooling the tube tosolidify the bonding metal and unite the interfaces.

9. The method of making tube from strip metal stock comprising, movingthe strip lengthwise and fashioning it into tubing of acircular crosssection with the strip edges in proximity with each other to form a seamarea having interfaces generally at the lowermost portion of the tube,the slope of the portions of the tube wall adjacent said seam area beingrelatively greater than that of the tube in its finished form,introducing a body of bonding metal into the tube interior as it isbeing formed, and, while utilizing the acircular shape of the tube as aguide means to maintain said seam area generally at its lowermostportion, passing the tube through a heating zone to melt the bondingmetal, so that the molten bonding metal gravitates to the seam area andflows by capillarity between the interfaces, with said portions of thetube wall adjacent said seam area forming a trough facilitating suchflow to said seam area, cooling the tube to solidify the bonding metaland unite the interfaces, and treating the tube to decrease said slopeof said wall portions and to change the acircular cross sectional formto a substantially round form.

References Cited in the file of this patent UNITED STATES PATENTS2,210,338 Quarnstrom Aug. 6, 1940 2,234,450 Quarnstrom Mar. l1, 19412,255,472 Quarnstrom Sept. 9, 1941 2,618,845 Quarnstrom Nov. 25, 1952

